Spiny Fleetfin

Surfscooters, the only surviving dolfinch, inherited the waters of their world after the end of the Mid-Ultimocene ice age. They colonized inland waters as well as the ocean, and some species even evolved some capacity to walk over land. Some are omnivores; a few mostly eat animal food. Yet the dolfinches have not retaken old roles as top predators in any of their environs; there are new hunters at the tops of the food chain now, highly formidable and threatening to all life beneath them: huge snarks now haunt the seas, and vertebrate life no longer rules the waters uncontested.

So the surfscooters, even as they grow, remain primarily plant-eating; but as the seas are now much deeper than they were, vegetation clusters sporadically along the edges of continental shelves. Aquatic puffgrass forms meadows blanketing sandy sediments, while large kelp-like algae forms colonies on rock sea coasts. In between these grazing grounds are wide stretches of barren - and dangerously exposed - open ocean.

The spiny fleetfin is the biggest dolfinch to live since the extinction of most of its relatives 10 million years ago, growing to over 21 feet long. It is almost totally herbivorous, feeding on water plants of many kinds, though it feeds incidentally on any small animals that happen to be living on those plants as well. Its neck is moderately long, and flexible enough to reach down and cut plants neatly near their base with its sharp, squared-off beak; in doing so, they are able to grow back from their roots, unlike if it pulled them up from the ground. The fleetfin chews its food with a very well-developed keratin tooth battery on its tongue and upper jaw; these pseudo-teeth are protected by a thick, pearly white layer of enamel and so are functionally indistinguishable from true teeth externally, though internally they develop more like claws that grow from within the mouth. Its teeth are shed and replaced every few weeks, with new ones emerging from the middle pushing out old ones at the edges, so that its mouth never wears down even as it chews a huge amount of sand while feeding. The fleetfins are well-adapted for long-distance movements from one patch of plants to another, even oceans away. They feed for a few weeks, storing the excess of calories as fat, and then when there is little left to keep them, they move on, fasting for weeks as they seek out new feeding grounds. 

Their flippers are long and pointed, jagged outlines on their trailing edge reduce drag in the water, carrying them quickly through the deep blue to find another vegetated coastal shelf to stop and feed. A small dorsal fin above the tail improves hydrodynamics on these journeys, as well as keeps it balanced as the creature swims. It moves in closely-bonded family pods of six to twenty adults, which keep tight formation to protect their calves and keep an eye out for each other, and which will defend their relatives with fierce aggression so that an enemy cannot take on just one; it must contend with them all. Yet there are some large, persistent predators now lurking in these waters - and they, too, may be social. So this group has evolved another set of defenses. Osteoderms both above and below the skin provide armor against biting jaws, making it difficult to puncture deep and cause lasting damage, at the cost of slowing their speed slightly over smaller fleetfin species. External, bony tubercles along the back and throat of the spiny fleetfin are especially prominent and are sharp like blades, allowing these dolfinches to angle themselves back against attackers to protect their soft underbellies and their young and even to swing their necks at enemies and cause offensive injuries. Very often they successfully drive off their attackers, which move on to easier prey.